Bats Think About Sex -- A Lot

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Bats may have more in common with the fictional Batman than
previously believed, since both successfully combine work with
courting sexy potential mates -- a lot of them.

A new study, published in the latest Proceedings of the Royal
Society B, reveals that bat echolocation calls, primarily used
for orientation and foraging, also contain information about sex,
which helps the flying mammals to acquire and keep mates.

The info is especially helpful to certain male bats with harems
of adoring females that are actually huskier than the males. This
holds true for the greater sac-winged bat (Saccopteryx
bilineata), which was the focus of the study.

Lead author Mirjam Knörnschild told Discovery News that "male
S. bilineata court females whenever the opportunity
arises. The social information in echolocation calls about the
sex of the calling bat benefits listening harem males because
they can distinguish between females and male rivals. It might
also benefit calling females because they are greeted friendly."

Knörnschild, a researcher at the University of Ulm's Institute of
Experimental Ecology, and her team analyzed greater sac-winged
bat echolocation calls. The scientists discovered that the calls
contain "pronounced vocal signatures encoding sex and individual
identity." This can include species identity, age, sex, group
affiliation, and other more specific information about the
individual.

Previously it was thought that bats just used echolocation to see
with sound, utilizing sonar to detect obstacles while in flight,
to find their way around in the dark, to help forage for food,
and for other essential purposes. Now it's known that this very
utilitarian system serves a dual function by facilitating
courtship and social communication in general.

Although females of this bat species are significantly larger
than males, their echolocation calls turns out to be higher
pitched and shorter. When played back to males, such calls led to
wooing with courtship vocalizations. When males heard the lower
pitched longer echolocation calls of other males, they responded
with the bat version of an aggressive rant.

Echolocation is only the latest known tool in the male bat's
impressive attraction arsenal.

She suspects that many, if not all, "bat species are capable of
encoding/extracting social information in and from echolocation
calls. The same is probably true for dolphins."

The study is only the latest to suggest that certain animal calls
are far more complex and info-rich than previously suspected.

Researchers studying bottlenose dolphins at Sarasota Bay, Fla.,
for example, determined that these marine mammals create
signature whistles for themselves that are comparable to human
names. Project leader Laela Sayigh, now with the Woods Hole
Oceanographic Institution, indicated it's possible that other
information, such as the age, sex and feelings of the dolphin,
may be encoded into each unique name-like whistle.

Dolphins were also recently found to hold formal greeting
ceremonies at sea, possibly electing an older respected
"spokesman" to handle particularly important encounters.

Greater sac-winged bats can also be compared to humans in at
least one respect. In an earlier study, Knörnschild and her
colleagues found that bat infants babble, mixing up echolocation
with courting trills and more. Such baby babbling is the first
known outside of primates.